| 摘要 |
PURPOSE:To prevent the runaway of a microcomputer system by providing a discriminating circuit outputting a control signal interrupting a power switch to the said power switch when a reset signal is interrupted within the initial reset time. CONSTITUTION:The initial reset circuit 2 outputs a reset signal (r) as soon as the power switch 4 is closed. The discriminating circuit 3 supervises the signal (r) from the circuit 2, and when the signal (r) is interrupted abnormally and the system is in ON-state, the circuit 3 detects it to input the switch control signal SW being an on-pulse having a width of T0 to the power switch 4 and to interrupt the power supply. A Vcc1 is applied to the circuit 3, which detects that a Vcc2 is turned off and outputs the signal SW having a width of T0 to the power switch 4. The state of the switch 4 is inverted and closed again. Through the repetition of operation above, when the circuit 3 discriminates that the reset signal (r) is interrupted continuously, the discrimination operation is stopped at a prescribed number of times, the signal SW is not outputted, the initial reset circuit 2 is regarded as a fault to leave the switch 4 interrupted. |
